Shredders of the type which are widely used to reduce metal objects such as automobile bodies into small manageable pieces are shown and described in the Newell U.S. Pat. No. 3,482,788. Such shredders include a housing, a rotary hammer assembly, means for rotating the hammer assembly, and a comb and grate bars which cooperate with the hammers to fragmentize or shred the objects.
The performance and efficiency of the Newell type shredder has been significantly improved by employing in the Newell housing a spider arm rotary hammer assembly such as shown in the Francis U.S. Pat. No. 3,727,848. As seen in the Francis patent, the ends of the spider arms are protected from premature wear by the replaceable protective caps.
The use of replaceable caps has reduced the downtime which resulted from excessive wear of the spider arms. However, significant downtime still can occur because of wear of other components by the rotor assembly, especially the end discs. The end discs are solid discs of metal positioned at each end of the hammer assembly which rotate with the rotary assembly and retain the shredded materials within the path of the hammers. The portion of the end disc which is especially subject to wear as the result of contact with shredded materials is its edge or periphery. Previous attempts to prolong the useful life of the end discs have comprised rebuilding the worn surfaces by sputtering metal thereon which is time consuming and thus costly or attempting to weld protective coverings on the disc. However, welding to the discs is undesirable because it can cause stresses in the metal which weaken the disc and/or the protective coverings.